EPW Forum

Hi dhw, I've switched units, and the two values are the same. You mean, with the same value of the smearing, the DOS with QE and EPW matched? If not, could you please share your scf,in, nscf.in (for the dos calculation using QE) and scf.in, nscf.in, and epw.in (for the epw calculation) files? Best, ...

Hi dhw,

Can you do a DOS calculation using QE with the mp smearing using the same smearing value from EPW? Please note that the unit of the smearing used in QE is Ry while in EPW is eV.

Best,
Hari Paudyal

Hi Makhail, Ans. 1. No, unfortunately. Ans. 2. Yes, you can tune fine k/q grids. I do not think the denser grids decrease the necessary wscut value. One thing I noticed is "Cutoff frequency wscut = 4.7690 and 3.9027". This looks very high to me now. Because of this, your calculation is taking a long...

Hi Mikhail, That's great. The only thing is that the higher the temperature I set in the calculation the more frequencies I need to make the gap positive. Is this normal behavior ? I think so. At the temperature close to Tc, the gap value will be low and may require a larger wscut. For all my previo...

Hi Sevenel,

Please make sure your "dvscf_dir='../save'" directory contains *.dyn_q*, *.dvscf_q*, and *.phsave/patterns.*.

Best,
Hari

Hi Makhail, One thing I am thinking right now is about 'wscut'. You have used 0.5 eV, can you say how did you pick this value? Is your maximum phonon frequency 205 meV? If yes, wscut = 0.5 eV is very low. You can do the following, 1) try increasing wscut (you can get an idea from the MgB2 calculatio...

Hi Nacy,

First, welcome to the EPW community.
Second, it would be helpful if you read the descriptions of input flags on the EPW website https://docs.epw-code.org/doc/Inputs.html

If you have any further specific questions, please let us know.

Happy EPWing,
Hari

Hi Mikhail, Numerically \Delta can have any values, we do not have any restriction in the code, however, a negative value of \Delta is not physical. I think the \Delta becomes negative if the following term is negative lambda(k, k', n-n') - muc* see eq. (22) of https://journals.aps.org/prb/abstract/...

Hi Mikhail, Could you please provide the following two plots/data? 1) The gap distribution function at every temps you have. 2) Scattered plot of \Delta_nk vs E- EF at every temps you have. This is the plot for example in MgB2, 5th, and 6th column of "MgB2.imag_aniso_gap_FS_15.00" at 15 K temp. Best...

Hi Mikhail, I think it can be correct. Your maximum value of the gap looks ~7 meV, and the way how the gap distribution is written is https://github.com/QEF/q-e/blob/03a7fa640903173662b24e4c30e520c9beaba16d/EPW/src/io_eliashberg.f90#L2039 to https://github.com/QEF/q-e/blob/03a7fa640903173662b24e4c30...